Vehicle fuel tanks for volatile hydrocarbon fuels such as gasoline normally contain a volume of liquid fuel and a volume of gas above the liquid fuel. Ambient temperature fluctuations lead to corresponding pressure fluctuations in the fuel tank. Excess pressure buildup in the fuel tank is reduced by a fuel tank venting system that vents fuel vapor out of a vent outlet of the fuel tank, collects and stores the fuel vapor in an activated carbon canister (ACC), and releases the fuel vapor downstream to an operating engine for combustion in the engine.
A liquid separator is placed in fluid communication between the fuel tank and the ACC to prevent carryover of a portion of the liquid fuel from the fuel tank to the ACC. Accordingly, the liquid separator separates and contains some liquid fuel and allows gaseous fuel vapor to pass to the ACC. But, from time to time, the liquid fuel must be transferred from the liquid separator back to the liquid fuel volume of the fuel tank to prevent the liquid separator from filling and blocking flow of gaseous fuel vapor therethrough.
There are three conventional solutions to this problem. First, the liquid separator may be located within the fuel tank and a fuel pump or a jet pump in the fuel tank may be placed in fluid communication with the liquid separator to discharge liquid fuel out of the liquid separator and into the liquid fuel volume of the fuel tank. Second, the liquid separator may be placed in an upper gaseous portion of the fuel tank interior and may include a bottom wall sloped toward a drain opening to discharge liquid fuel by gravity. Third, the liquid separator may be placed above the fuel tank such that a drain port of the liquid separator is higher than the vapor outlet of the fuel tank so that the liquid separator drains liquid fuel to the fuel tank under the force of gravity.